At a Wednesday news conference, they said the incidents have to stop, and any future flash mobs will be met with organized and relentless crackdowns by police.

"This is an issue of citywide significance and importance. It's affects all Philadelphians regardless of neighborhood, regardless of community," Mayor Nutter said.

To that end, city officials outlined a plan to fight back against the flash mobs:

There will be tougher curfew enforcement for those under 18 years old on Friday and Saturday nights.

There will be more hard line prosecution by the district attorney

There will be more uniformed and undercover police during high-risk hours in known hotspots.

There will be non-stop monitoring of social networks.

The Mayor explained there will be continued enforcement of the citywide curfew currently in place for youth ages seventeen and under, 10:30 pm to 6:00 am on weekdays and 12:00 am to 6:00 am on weekends.

Nutter went on to say he reserved the authority to declare an immediate, expanded curfew if necessary.

Mayor Nutter also directly addressed the young people participating in the flash mobs.

"Stop the stupidity. Cut it out," he said. "We're not messing around and you and your parent are going to find yourself in serious trouble if we have any more of this kind of activity in the City of Philadelphia."

Nutter also addressed the parents, saying they will be held responsible for their child's behavior.

He said state law provides the court "with the power to order a parent, guardian or custodian to participate in the treatment, supervision or rehabilitation of a child." Nutter explained that could mean a parent would have to do community service, pay restitution, go to counseling, treatment or education programs.

Police say 3,000 teenagers from all around the city converged on South Street to take part in the flash mob.

Action News has obtained graphic video of the violence over the weekend along South Street and it is disturbing. But it does give us the clearest picture yet of the utter chaos that broke out.

Within seconds the mob was fighting and knocking down pedestrians to the ground and then jumping people in a car that was passing by.

The video shows the violence causing serious injury to at least two people.

The incident is the latest in a rash of flash mob incidents on South Street and Center City including the one that broke out at the Gallery last November and was posted on the internet.

Philadelphia Police Commissioner Charles Ramsey said this kind of behavior by young people, some as young as 11-years-old, has got to stop.

"This is not 'Leave it to Beaver' type stuff were talking about here. We are talking about serious crimes being committed and people being injured. If anybody thinks that's a joke, well, they got another thing coming."

Psychologist and author Dr. Michael Bradley said teenage social behavior in the age of internet social websites is troubling ingredients for bizarre impulsive social behavior.

"We're seeing these kinds of bizarre expressions of teen impulsivity, bad judgment, inability to understand consequences of their actions with the new technology which allows them... to express these things in very dangerous ways," he said.

Action News is monitoring internet traffic suggesting that there are more flash mob incidents being planned for this weekend.

Alleged participants in previous flash mobs in court

Meanwhile, more than a dozen teens pleaded guilty to felony rioting charges and two others were convicted for being part of a roving mob in Family Court on Tuesday.

Judge Kevin Dougherty sentenced 18 juveniles in connection with an unruly gathering of as many as 100 teens on March 3.